Drive mechanism for elevator door

ABSTRACT

An elevator car has a drive mechanism mounted in a compact housing on the upper surface of the car. The drive mechanism includes a rotatable drive shaft, around which is mounted a linear actuator block having a plurality of ball bearings, obliquely arranged relative to the shaft, and firmly touching the shaft. Rotation of the shaft by a motor makes the block move linearly along the shaft. A bracket attached to the block carries an elevator door. Rotation of the shaft therefore opens and closes the door. The direction of movement of the block, and hence the door, depends on the direction of rotation of the shaft. The drive mechanism is compact and simple, and can be applied to new elevators or can be used to retrofit existing elevator cars.

BACKGROUND OF THE INVENTION

This invention relates to the field of elevators, and, in particular,provides an elevator car having an improved mechanism for controllingthe elevator door.

The elevator doors of the prior art are powered by a motor mounted abovethe elevator car. An elaborate set of pulleys and linkages provides aconnection between the motor and the door. In commercial elevators,there are generally two doors, an inner door and an outer door.

The arrangement used in commercial elevators of the prior art is noteconomical for use in residential elevators. The components of theelevator are heavy and bulky. In the event of a power failure, it isvery difficult to open the elevator door.

Elevators used in residential environments are generally smaller andsimpler than their commercial counterparts. There is a need for asimple, reliable, and relatively inexpensive drive mechanism for thedoor. The present invention provides such a mechanism. With the elevatordoor of the present invention, one can easily open the door manually inthe event of a power failure. The construction of the elevator door ofthe present invention is simple, comparatively inexpensive, and safe.

The door mechanism of the present invention also has the advantage thatit is highly modular, and can be used to retrofit existing elevatorshaving a variety of configurations. The present invention issufficiently compact for use in a residential elevator, but it couldalso be used in commercial applications.

SUMMARY OF THE INVENTION

The present invention comprises an elevator car having a drive mechanismattached to the upper surface of the car housing. A sliding door formsone of the walls of the car. The drive mechanism includes a rotatableshaft, a motor or other means for rotating the shaft, and a block havingrecesses which hold a plurality of ball bearings. The ball bearings aremounted within the block at an angle such that when the block is mountedaround the shaft, rotation of the shaft causes the bearings to rotatealso. Due to the orientation of the ball bearings, the block moveslinearly along the shaft when the bearings rotate. Reversing thedirection of rotation of the shaft reverses the direction of linearmovement of the block. The block carries a bracket to which is attachedone end of the sliding door of the elevator car. Thus by rotating theshaft, one opens and closes the sliding elevator door.

In the preferred embodiment, all the elements of the drive mechanism arecontained within a single drive housing. These elements include themotor which drives the shaft, a belt and pulley connecting the motor tothe shaft, and an electronic control module which governs the operationof the motor and thus controls the movement of the door. Due to itsmodular construction, the present invention can be used to retrofitexisting elevator cars with the new drive mechanism. Also, it can beeasily installed as original equipment with a minimum of expense andeffort.

The present invention therefore has a primary object of providing animproved drive mechanism for an elevator door.

The invention has the further object of providing a drive mechanismwhich reduces the cost and complexity of an elevator door.

The invention has the further object of providing a door drive mechanismwhich is especially desirable for use in residential elevators.

The invention has the further object of providing a drive mechanism foran elevator door, which mechanism can be easily installed on existingelevators.

The invention has the further object of providing an elevator door drivemechanism of modular construction.

The reader skilled in the art will recognize other objects andadvantages of the present invention, from a reading of the followingbrief description of the drawings, the detailed description of theinvention, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a perspective view of an elevator car of the presentinvention, with the drive mechanism affixed to the upper exteriorsurface of the car.

FIG. 2 provides a perspective view of the drive mechanism for theelevator car.

FIG. 3 provides a fragmentary cross-sectional view, taken along the line3--3 of FIG. 1, and showing the block which carries the bracket to whichthe elevator door is attached, in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a perspective view of an elevator car made according to thepresent invention. The elevator car includes housing 1 having an uppersurface 3. Drive mechanism 5 is mounted to the upper surface of thehousing. An elevator door 7 forms one wall of the elevator car. In theembodiment shown in FIG. 1, the door comprises a plurality ofarticulated panels which fold in a zig-zag manner when the door isopened. The door panels slide within track 9, and also within a similartrack, not visible in FIG. 1, near the upper portion of the car. Notethat the invention can be practiced with many other kinds of slidingdoors, and is not limited to the particular folding and sliding doorshown in FIG. 1.

The drive mechanism 5 can be best understood with reference to theperspective view of FIG. 2, which shows the drive mechanism without theelevator car. All of the components of the drive mechanism are containedwithin drive housing 11, which shields the working components from view.A rotatable shaft 13 extends substantially across the width of the car.FIG. 2 shows the shaft in fragmentary form, so as to illustrate theother components; FIG. 1 shows substantially the entire shaft. Linearactuator block 15 fits around shaft 13 and moves along the shaft, in amanner to be described. Bracket 17 is attached to block 15. The otherend of the bracket can then be attached to the elevator door.

Motor 19 causes rotation of shaft 13, by means of belt 21 and pulley 23.Any motor can be used, provided that it is reversible, so that shaft 13can be made to rotate in both directions. Limit switches 25, 27, and 29are actuated by a suitable cam (not shown) attached to block 15.Actuation of limit switch 25 indicates that the elevator door is open.Actuation of limit switch 29 indicates that the door is closed.Actuation of limit switch 27 indicates that the door is nearly closedand provides a signal that can be used to begin deceleration of thedoor. Electronic control module 31 controls the operation of the door.The control module receives inputs from the limit switches, and fromsuitable switches on the outside of the car indicating arrival at aparticular floor.

The control module causes the door to open and close in the desiredmanner. For example, one can program the control module, either bysoftware or by hard-wiring, to hold the door open until receipt of asignal from the car, or from an elevator call button on another floor.When such a signal is received, the gate automatically closes, andreopens when the elevator car arrives at the selected floor.

The electronic control module can also contain various controls forsetting certain parameters of operation. For example, one can set thespeed at which the elevator door opens, the speed at which it closesinitially, and the speed to which it decelerates when the door is nearlyfully closed. As a safety feature, the door can also be programmed toopen when an obstruction (such as a person or a hand) is detected in thepath of the closing door. One can control the amount of time the cardoor will remain open after it reopens upon detection of such anobstruction. Also, one can control the amount of obstructive force whichthe closing door must detect before it will abandon its attempt to closeand reverse direction. Other such controls can be added; in FIG. 2, theillustration of the control module is intended to be symbolic of variouscontrol functions, all of which are preferably controlled through asingle module.

FIG. 3 shows more details of the structure of the linear actuator block15 and its connection to the elevator door. As shown in FIG. 3, thebottom portion of drive housing 11 is attached to the upper surface 3 ofthe elevator car housing 1. The linear actuator block 15 is attached tothe drive housing by suitable bolts, and is also connected to bracket17. The bracket is what is connected to elevator door 7. FIG. 3 showsbolts 39 which secure the bracket to the door 7. However, any othermeans of connection of the bracket to the door can be used. As shown inthe figure, the elevator door is attached to rollers 33 which ride intrack 35. Thus, in the embodiment shown, the door moves within bothupper and lower tracks. The configuration of tracks can be changed,within the scope of the invention. It is possible, though notpreferable, to omit the lower track entirely, for example. What isimportant is that the drive mechanism have an attachment to the door.

As shown in FIG. 3, block 15 defines a housing for ball bearings 37which are arranged around shaft 13, so as to touch the shaft. The ballbearings are all disposed at an angle to the shaft, as shown. Becausethe ball bearings and the shaft are in firm contact, rotation of theshaft causes rotation of the bearings. Due to the oblique orientation ofthe bearings, rotation of the bearings generates a force having acomponent which is directed along the length of the shaft. The result isthat when the bearings rotate, due to rotation of the shaft, the blockmoves linearly along the shaft. The direction of rotation of the shaftcontrols the direction of movement of the block along the shaft. Themoving block carries with it the bracket 17, and hence the elevatordoor. A linear actuator of this type, i.e. a combination of shaft andactuator block, can be obtained commercially. For example, one suchlinear actuator is sold under the trademark Roh'lix by the Barry WrightCorporation.

The elevator made according to the present invention has importantadvantages over elevators of the prior art. It is economical,structurally simple, and compact. All of its components can be housed inthe relatively compact drive housing 11, shown in the figures. Inelevators of the prior art, the motor is generally mounted above thecar, and the other components take considerably more space than thatrequired by the present invention.

Due to the compact structure of the drive mechanism, the entire devicecan be sold as a self-contained module. One can retrofit an existingelevator car with the drive mechanism of the present invention, simplyby mounting the drive mechanism to the car and connecting the bracket tothe door. The compact structure reduces or eliminates the need foradditional overhead clearances that would be necessary with elevatorcars of the prior art. The present invention is advantageous also whenthe elevator is being manufactured as original equipment, because thesame considerations mentioned above still apply.

The linear actuator drive has the advantage of simplicity andreliability, as it significantly reduces the number of belts, gears,linkages, and/or clutches that would otherwise be necessary to connect adrive motor to an elevator door. With the elevator car of the presentinvention, one need only provide rotational motion to a single shaft,and the elevator door moves accordingly, under the influence of frictionbetween the rotating shaft and a set of ball bearings. Moreover, in theevent of a power failure, one can easily open or close the doormanually, since the ball bearings will also slide freely along theshaft. Manual opening or closing of the door cannot harm the motor,since it is necessary only to slide the bearings along the shaft, andsuch sliding motion does not affect the motor.

While an elevator door is closing, one needs to provide for automaticreversal in the event an obstruction is detected. The present inventionmakes it easy to provide for such automatic reversal. One can simplymonitor the torque of the motor; when the torque exceeds a predeterminedvalue, as would occur if an obstruction blocks the door, the controllerreverses the direction of the motor and opens the door.

The above-described embodiments should not be interpreted to limit theinvention. One can modify the invention in many ways. The specific shapeof the elevator car and the door can be changed. The particularfunctions of the electronic controls can be modified. The invention canbe practiced with a variety of types of doors. The only importantrequirement for the door is that it can be opened and closed by linearmovement of a component traveling along a shaft disposed across thewidth of the car. These and other modifications, as will be apparent tothose skilled in the art, should be considered within the spirit andscope of the following claims.

What is claimed is:
 1. An elevator car comprising:a) means defining acar housing, the housing having an upper portion, b) a drive mechanismmounted to the upper portion of the housing, the drive mechanismincluding a rotatable shaft, means for rotating the shaft, a blockdefining recesses which contain at least one rollable bearing, thebearing being fixedly mounted in the block and the block being mountedon the shaft such that rotation of the shaft causes the block to slidealong the shaft, the block having a bracket attached thereto, whereinthe bearing contacts the shaft with a pressure which is substantiallyuniform for any position of the block along the shaft, and c) a slidingdoor, at least a portion of the door being attached to the bracket,wherein rotation of the shaft causes opening and closing of the door. 2.The elevator car of claim 1, wherein the rotating means comprises amotor connected to the shaft by a pulley.
 3. The elevator car of claim1, wherein the rotation of the shaft is controlled by an electroniccontrol module.
 4. The elevator car of claim 1, wherein the rotatingmeans comprises a motor connected to the shaft by a pulley, and whereinthe rotation of the shaft is controlled by an electronic control module,and wherein the motor, the pulley, and the control module are allcontained within a single drive housing.
 5. In an elevator car, the carincluding a housing, a sliding door, and a drive mechanism for movingthe door, the improvement wherein the drive mechanism comprises arotatable shaft, means for rotating the shaft, a block defining recesseswhich contain at least one rollable bearing, the bearing being fixedlymounted in the block and the block being mounted on the shaft such thatrotation of the shaft causes the block to slide along the shaft, theblock having a bracket attached thereto, wherein the bearing contactsthe shaft with a pressure which is substantially uniform for anyposition of the block along the shaft, and the door being attached tothe bracket, wherein rotation of the shaft causes the door to open andclose.
 6. The improvement of claim 5, wherein the rotating meanscomprises a motor connected to the shaft by a pulley.
 7. The elevatorcar of claim 5, wherein the rotation of the shaft is controlled by anelectronic control module.
 8. The elevator car of claim 5, wherein therotating means comprises a motor connected to the shaft by a pulley, andwherein the rotation of the shaft is controlled by an electronic controlmodule, and wherein the motor, the pulley, and the control module areall contained within a single drive housing.
 9. In an elevator car, thecar including a housing, a sliding door, and a drive mechanism formoving the door, the improvement wherein:the drive mechanism iscontained within a module which is removably attached to the housing,the module includes a rotatable shaft, means for rotating the shaft, ablock defining recesses which contain at least one rollable bearing, thebearing being fixedly mounted in the block, the block being mounted onthe shaft such that rotation of the shaft causes the block to slidealong the shaft, the block having a bracket attached thereto, thebracket extending from the module, wherein the bearing contacts theshaft with a pressure which is substantially uniform for any position ofthe block along the shaft, and wherein the door is attached to thebracket.
 10. A method of retrofitting an elevator car with a drivemechanism, the elevator car having a housing and a slidable door, themethod comprising the steps of:a) providing a module which includes arotatable shaft, means for rotating the shaft, a block defining recesseswhich contain at least one rollable bearing, the bearing being fixedlymounted in the block and the block being mounted on the shaft such thatrotation of the shaft causes the block to slide along the shaft, theblock having a bracket attached thereto and extending from the module,wherein the bearing contacts the shaft with a pressure which issubstantially uniform for any position of the block along the shaft, b)mounting the module to the housing, and c) connecting the bracket to thedoor.